The major waste product from the steelmaking practice is slag. In iron- and steelmaking, nearly 12 Mt of steelmaking slag is produced every year in Europe (around 50 Mt in the world). The most widespread approach to recover the values existing as inclusions in the slag matrix in steelmaking slags is to crush the slag at ambient temperature, separate metallic iron by magnetic separation and recycle the same by introducing it in steelmaking process. The remains are often used as filling materials in road and waterway construction. A significant amount of the slag remains in dumps, which damages the environment and requires a land for secure storage.
The article “Confocal Microscopic Studies on Evolution of Crystals During Oxidation of the FeO—CaO—SiO2-MnO Slags”, Metallurgical and Materials Transactions B, suggested that MnFe2O4 and Fe3O4 could be recovered from slags comprising FeO, CaO, SiO2 and MnO under oxidizing conditions. MnFe2O4 and Fe3O4 were found to precipitate as spinels in sizes between 1-50 μm.
A number of methods to produce nano sized spinel-type manganese ferrite have been suggested. For instance Nano-sized manganese ferrite (MnFe2O4) powder has been synthesized via coprecipitation method, using FeSO4.7H2O and MnSO4.H2O as starting materials. No methods have been suggested to produce nano sized spinel-type manganese ferrite from metallurgical slags.